300 Watts ET tear down

• Manufacturer: Relco Italy• Model: DINO CC300 S• Power: Min 100 W , max 300W• 230 - 240 V AC input• 12 V DC output• Double output from both sides of the housing

300 Watt Electronic Transformer

Top view

M1: 230 VAC, 60 Hz input M3, M4: 12 V DC outputL3: Output transformer with center tap secondary

L3

L2

Q4,Q5

Q6,Q7

M3

M4

L4

M1

Q3,Q2

Center tap on secondary

M4

Bottom view

IR2161S Diode bridge

Input terminals, 230 V AC

Output transformer input

Transformer output

Q4Q5

Gate drive circuit for Q6,Q7

Gate drive circuit for Q4,Q5

Q6Q7

12 V DC output (M3)

12 V DC output (M4)

Schematic

A clear schematic with components values visible has been drawn in Visio.

Output Transformer

Primary: 2 parallel wires of 0.74 mm 60 Turns, Total: 120 turns

Secondary: Center-tap double output. Litz wire made up of 80 strands of 0.11mm wire 3 turns of 4 parallel Litz wire wound on each winding Total: 12 turns

Core: EE55 core

Litz wire secondary

Other magnetic components

L1 : 29 turns of 0.48 mm wire OD: 14.34 ID: 8.03 Height: 2.34 green ferrite core

L2: 140 turns of 0.67 mm OD: 24.23 ID: 13.97 Height: 8.22 yellow core

L4: 8 turns of 2.4 mm OD: 26.73 ID : 14.53 Height: 11.38

IC 2161S• Very different circuit from conventional ET -- No saturable transformer. -- No DIAC to initially start the circuit operation.• Everything taken care of by International Rectifier IC 2161S

Source: IR product datasheet

Understanding basic IC operation - Modes

• Under-voltage lockout mode• When the chip VCC is below threshold.• Guarantees that IC is fully operational before HO and LO are activated.• RS, RD, CD - critical design components. • Charge pump(Voltage doubler) connected to circuit for VCC after startup.• DB and CB are for supplying power to high side driver circuit.

Modes of operation

• Soft-start mode• Inrush current under cold filament condition can trigger shut down protection.• The frequency is kept high (133kHz) when IC just starts oscillating - this allows less voltage, less current in

the lamp which eases the inrush current.• CSD connected to soft-start circuit.

Modes of operation

• Run Mode ( Voltage compensation mode).• Frequency variation required to compensate the output voltage at varying load.• CSD connected to Voltage compensation circuit.• Load current sensed by RCS (at the source of Q2) and reflected as voltage at CSD.• VSD = 5V at full load and 0V at no load.• In run mode, Oscillator frequency varies from 34kHz at full load to 70kHz at zero load.

Typical waveforms

VCC pin voltage

CSD voltage• At 100 W• 0 to 5 V in soft-start mode in 0.264

sec.• In run mode, average value = 0.911

volt

Run mode

Soft-start mode for 0.264 sec

CSD voltage• At 150 W• 0 to 5 V in soft-start mode in 0.292

sec.• In run mode, average value = 1.78

volt

Run mode

Soft-start mode for 0.264 sec

CSD voltage

• At 300 W (full load)• 0 to 5 V in soft-start mode in 0.0428

sec.• In run mode, average value = 4.69

volt

Run mode

Soft-start mode for 0.0428 sec

Transition from soft-start mode to Run mode

Frequency variation with load

Load (W) Frequency (kHz)

10 69.44

20 68.49

50 63.69

100 59.8

150 55.55

200 48

300 34

Soft-start mode waveform

Input voltage to transformer

High frequency ( 125 kHz ) initially due to soft-start

• Input waveform transformer switched at high frequency initially

• At 200 W load, initial frequency = 125 kHz

• At run mode, frequency reduces to 48 kHz